1. Technical Field
This invention relates to Winchester type (hard drive) disk drive systems and more particularly to a system and method for protecting data stored on a disk in a disk drive system from loss as a result of mechanical shock to the system. Still more particularly, the invention relates to preventing data loss in disk drive systems as a consequence of failure of a magnetic head to remain on track during a write operation.
2. Description of the Related Art
A disk drive is an information storage device which utilizes at least one rotatable magnetic disk to store information. The information is represented on the disk as a series a magnetically polarized regions. The magnetic regions are arrayed along the surface of the disk along either a plurality of concentric data tracks or spiral data tracks.
A transducer reads information from or writes information to the various tracks on the disk while the disk moves underneath the transducer. The transducer forms a portion of a "head" which is attached to a slider. The slider is a carrier body which "flies" just off the surface of the disk. The slider is attached on its backside to a suspension system which in turn is connected to an actuator arm. The actuator arm is used to selectively position the head over one particular desired track during a read or write operation. The disk is spun bringing the magnetically polarized regions by the head one after another. The slider itself may be moved radially inward or outward to change the track over which the slider is positioned.
The rotation of the disk results in the relative movement between a surface of the disk and the slider. In a so called hard drive, this in turn creates a cushion of air between the disk and the slider forcing the slider and the disk apart. Separation of the slider and disk reduces wear and consequent premature destruction of the components. The face of the slider toward the disk is known as the air bearing surface. The suspension system provides dimensional stability between the slider and the actuator arm by compensating for the force of the air between the air bearing surface and the disk surface as well as providing rapid motion damping of the slider following its repositioning from one track to another. The suspension system should control slider position relative to its directions of motion between tracks while resisting out-of-plane movement relative the preferred "fly height", i.e. the spacing between slider and disk surface. At no time during data read or write operations of the drive should the slider come into contact with the disk surface.
The suspension typically comprises a load beam attached to the actuator arm and a flexure which connects the slider to the load beam. The load beam balances the slider by counteracting the lifting force from the spinning disk. The flexure supports the slider and allows flexibility during the slider's ride on the cushion of air.
Design of the slider air bearing surface, the suspension system and the actuator arm are directed to achieving a low mass and a high degree of positional stability in a selected position. In doing so the designers must take into account a number of factors. For example, lift from the air cushion between slider and disk change as the slider is moved radially over the disk by the actuator arm and the relative speed of the slider over the disk changes. Where the slider is mounted on a rotary actuator arm (having a movement similar to the tone arm of a phonograph player), the slider rotates relative to its track over the disk changing the interaction between the air bearing surface and the air cushion. However, all of these problems are vastly complicated by the possibility of exposure of the disk drive to mechanical shock. The actuator, being by its nature a movable device, will tend to lag behind the magnetic disks, thereby throwing the head and track out of alignment.
In most computers, for example, floor or desk top personal computers, severe shocks tend to be rare. In addition, the disk drive can be protected from some shocks by mounting it in the computer surrounded by shock absorbing material. In increasingly popular portable computers, the possibility of mechanical shock is greater. Such computers are frequently used "on the move" in vehicles or in crowded locations where the occurrence of mechanical shocks is more frequent. If such a shock occurs during a write operation, and the head is left off track, two undesirable things can result. One is that the data being written will not be in the desired location, but may be split between the desired track and adjacent tracks, or lost between tracks. The second undesirable result is that data previously recorded on the tracks adjacent to the target track may be partly overwritten.
A portable computer, due to energy requirements and space limitations generally will rarely provide common backup tools such as a tape drive and certainly will not have access to more esoteric data storage systems such as parallel arrays of independent disk drives (RAID systems) affording the possibility of distributed storage of data among a plurality of disk drives with sophisticated error recovery systems using such distribution. Even were a system such as RAID available, all of the drives would be part of one package in a portable computer and thus all would be exposed to the same mechanical shocks.
It is an object of the invention to provide a method of operating a Winchester type disk drive system in a portable computer providing for protecting data stored on a disk in a disk drive system.
It is still another object of the invention to prevent loss of data as a consequence of failure of a magnetic head to remain on track during a write operation.
It is yet another object of the invention to prevent data loss in disk drive systems as a result of mechanical shock to the system.